... 2 2ar OA= = ; 2 2 2 2 2 26 2 3 2 2 2 2 2 a a a al SA SO AO a = = + = + = + = ÷ ÷ ÷ ÷ 2 xqa 2 S rl a 2 a 2 ⇒ = π = π = π (đvdt)0 .25 0 .25 0 .25 0 .25 0 .25 0 .25 0.5Ví ... h=R= 2 2a=l ⇒ Sxq = 2 2 2 2 2R .a . a aπ = π = πl ⇒ Stp = Sxq + Sđáy = 2 2 2 2 2 2 (2 2 2) a a aπ π π+ = + b) V = 3 2 21 1 2 2 2 23 3 3aR h . a .aππ = π = Ví d ụ 2. 7 ... 33 2 a1 .20 . R=46a,S= 2 .3 2 aπ.V=86.3aπ1 .21 . R=36a,S=3.8 2 aπV= 27 6.83aπ1 .22 . V=433a1 .23 . V=33a, h = 2 aPh ần II 2. 1. 2 70xqS aπ=,3175V aπ= 2. 2....